Fundamental and Derived Quantities

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Fundamental Quantity

A fundamental quantity is a quantity from which other quantities may be derived; for example, length and time are fundamental quantities from which a quantity such as speed is derived.

From the 1960's the system of units used in the scientific community was the International System (S.I.) of units, SI Units. The S.I. System of units is based on seven (7) fundamental quantities as seen Table 1 below.

Definitions:

1. Mass - is the amount of substance or material in an object.
2. Length - is the distance between two points.
3. Time - is the duration between two instants or events.
4. Current - is the flow of electrons from a high potential to a low potential.
5. Temperature - is the measure of how hot or cold an object or substance is based on a comparative scale.
6. Amount of Substance - is a measure of the amount of elementary entities such as atoms, molecules and other particles.
7. Luminous Intensity - is a measure of the amount of light that a point source radiates in a given direction. 

Derived Quantity

A derived quantity is produced when two (2) or more fundamental quantities are combined, either by multiplication or division as shown in Table 2 below.

Definitions:

1. Displacement - is how far off an object is from its rest position, usually a straight line distance.
2. Speed - is how fast an object is moving.
3. Velocity - is how fast an object is moving in a specific direction.
4. Acceleration - is the change in velocity of a period of time. Acceleration could be positive, negative (retardation) or zero (no change in velocity).
5. Force - is a push or a pull which may speed up, slow down, change direction or shape of an object.
6. Energy - is the ability to do work.
7. Density - is the amount of matter in a given volume of an object or substance.
8. Moment - is the turning effect of a Force.
9. Power - is the rate at which work is done.
10. Work - is a force of 1 N displacing an object by 1 m in the direction of the force.
11. Momentum - is the quantity of motion of a moving body, measured as a product of an object's mass and velocity.
12. Pressure - is the force acting on a surface per unit area.